Do winglets provide the same benfits on propellers as they do on wings?

From : Don Stackhouse

Well, um... if you mean "minuscule benefits if any at all, and in many cases a net loss", then I'd have to say yes. In general, they can help propellers, but the amount of benefit has to be balanced against the structural issues, which can be considerable unless the winglets are extremely small. As with winglets, it will depend on the specific prop design in question, especially the disk loading (the prop equivalent of wing loading).

They have been studied, with mixed results. I heard some rumors of a study of some fairly large "proplets" in a wind tunnel at Purdue University quite some years ago, and some rumors of some fairly spectacular structural failures that resulted, but I can't confirm that.

Probably the best known example of some sort of winglet device on a propeller are the Hartzell "Q-tip" props (Prince propeller also has their "P-tip" knock-off, a blatant infringement of Hartzell's patent). The Hartzell Q-tip props have about the last inch of each blade bent aft 90 degrees. This reduces the diameter by about two inches. In general they provide little or no net change in performance, the reduction in diameter offsetting any benefits from whatever winglet effects may or may not exist. It does seem to depend quite a bit on the details of each specific aircraft type, as well as the flight condition in question (a lot like winglets in this regard). In general, they seem to be the most net benefit (or the least net loss) at high power and low airspeed. However, the reduction in diameter reduces the tip speed, which can reduce noise.

There are two applications that seem to measurably benefit from Q-tip props. The main one is on twin-engined airplanes that have very little clearance between the blade tips and the sides of the fuselage. In at least some cases, Q-tipping the prop allows a 2" reduction in diameter, with no significant loss of performance. However, this reduction increases the clearance betwen the prop tips and the fuselage (for example, if it was 4" before, Q-tipping increases that to 5", a 25% improvement), which can in at least some cases result in a very significant improvement in the noise level in the passenger cabin.

The other case that seems to benefit is in bush planes that operate from gravel runways. The tip vortices from the Q-tips don't seem to scoop up as much dirt and gravel (which does strongly suggest that they do in fact significantly alter the tip vortex), which results in significantly less wear on the outer portions of the blades.

Don Stackhouse
DJ Aerotech